In my prior applications, op. cit., I describe using a portable NMR instrument so that flow properties of rock samples can be accurately and swiftly measured, especially at remote field sites. The described principle of operation:spin-lattice relaxation times of fluids in chip samples, can be accurately correlated with flow properties of different rock samples. However, in a limited number of occasions related exclusively to field use of newer instruments, problems have arisen. These problems relate mainly to the fact that such instruments do not have the operating characteristics on which I based my prior advances: large DC field inhomogeneity and unusual background phase incoherence. In such instruments, I now find that at least one of the above-mentioned inherent conditions has been eliminated.